I don't think that anyone will be able to answer your request here. Your question is basically "How do I create a whole and complete network(!) that a) connects HYTERA repeaters, b) connects MMDVM repeaters and MMDVM hotspots, and c) enables access via smartphone and how bring it all together. The detailed answer could fill a whole book :)
Therefore I will limit my answer to the content of this thread - Hytera DMR Gateway.
The background: HYTERA repeater like RD985 or RD625 have their own protocol to connect these devices over IP. It's not compatible with the MMDVM-protocol. If you want to connect your HYTERA-repeater to a MMDVM-based System (aka DMR-master) like HBlink you need a protocol converter. It works like that:
HYTERA-repeater <-> gw_hytera_mmdvm <-> DMRGateway (G4KLX) <-> one or multiple DMR networks. For the two tools in the middle, gw_hytera_mmdvm and DMRGateway the best solution is a Pi. The repeater connects the Pi running gw_hytera_mmdvm, that tool is connected internally via 127.0.0.1 with the DMRGateway and the DMRGateway itself connects one or more MMDVM-based access systems like HBlink or similar like IPSC2-server or BrandMeister-server. So you will have a protocol converter from HYTERAs IPSC to/from MMDVM. Nothing more, nothing less.
To bring all systems together, you need to setup a dmr-master like hblink - and then you can connect your systems like mmdvm-hotspots, mmdvm-repeaters and of course your HYTERA repeaters with gw_hytera_mmdvm and DMRGateway. Your smartphone access (maybe with DVSwitch mobile and it's own opportunities) you need to connect to the master system like Hblink too. It is impossible to present all of this as a complete guide. This will not be a manual, it will be a book :)
Yes, I have running such a complete solution include HYTERA-repeaters. It's possible and work very well. Dozens of hours of work are required before all of this is done. What it is not: a small and quick solution.
Btw, a downgrade from FW 9.xx to 8.xx is NOT supported by HYTERA.The background was the lost court case against MOTOROLA, as a result of which HYTERA had to remove some things from the firmware with the start of version 9.xx.
73 Heiko, DL1BZ